A software framework for easily writing applications which process vast
amounts of data (multi-terabyte data-sets) parallelly on large clusters
(thousands of nodes) built of commodity hardware in a reliable, fault-tolerant
manner.

AbstractMapWritable
Abstract base class for MapWritable and SortedMapWritable
Unlike org.apache.nutch.crawl.MapWritable, this class allows creation of
MapWritable<Writable, MapWritable> so the CLASS_TO_ID and ID_TO_CLASS
maps travel with the class instead of being static.

Client.call(Writable param,
InetSocketAddress addr,
Class<?> protocol,
UserGroupInformation ticket,
int rpcTimeout,
Configuration conf)
Make a call, passing param, to the IPC server running at
address which is servicing the protocol protocol,
with the ticket credentials, rpcTimeout as timeout
and conf as configuration for this connection, returning the
value.

Client.call(Writable param,
InetSocketAddress addr,
Class<?> protocol,
UserGroupInformation ticket,
int rpcTimeout,
Configuration conf)
Make a call, passing param, to the IPC server running at
address which is servicing the protocol protocol,
with the ticket credentials, rpcTimeout as timeout
and conf as configuration for this connection, returning the
value.